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Old 07-10-2017, 05:38 PM   #1
Crazygirl
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Transmission making me Crazy....

So, I have already posted on a different thread about some other issues I am working through with my 2002 Trailblazer LT. I believe the engine is 4.2l, and has almost 180k miles.
I thought the transmission was unhappy because there was no fluid to be found on the dipstick when I bought the car, so we put fluid in and removed the code P1870 that caused my SES light to come on. However, the following day, the light and code came back.
So yesterday my hubby climbs under it and sees that a bolt is missing and all of the other bolts on the transmission pan were loose, allowing tranny fluid to spray all over the cat converter. We thought taking care of the bolts would take care of the problem. Still a big, fat NO.
When it's first driven, it seems to be okay. Shifts up and down smoothly, like it should. However, driving it for about 15 minutes seems to activate some demon, because then the shifts, especially the lower ones, are hard thunks. It's like riding a roller coaster. Plus, the longer it's driven, the more it seems like there is a shudder to the vehicle.
It keeps throwing the same code, P1870, and the reader says $10. We have picked up a transmission control solenoid and hope that replacing it may finally solve this, but I'm doubtful. I'm concerned we'll need to replace the entire control valve body, or even worse, rebuild or replace the entire transmission.
On top of that, the engine is making a ticking kind of sound that my husband says is some kind of actuator trying to kick in; he says it's likely an A/C actuator since we have also had the A/C system repaired, but the place that did the work said they couldn't get to the driver's side actuator without taking apart the entire dash, and to just close the driver's side air vents and just use the passenger side.
To be honest, I'm afraid to drive it and I just got the stupid thing. I really do want to keep it, but don't want to spend a couple of thousand more dollars on a new transmission. Please help....
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Old 07-10-2017, 06:55 PM   #2
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Re: Transmission making me Crazy....

If you have your electrical problems resolved, drop the pan, pull the filter, inspect the pan for excessive metal, inspect the filter pad for metal, and check all the electrical connectors. You can change the PCS if you like, but the high line pressure may be a symptom rather than a cause. When the PCM detects a generic transmission slip problem (P1870) if will usually command full line pressure to compensate, and it sounds like your PSC is doing exactly what it is told.

It would also be a good time to install a drain plug in the trans pan so that future fluid changes are easier.cleaner. And there may be several future changes to clean out the trans and potentially restore operation.

Of course, if you find glitter when the pan is removed the game may be over already.
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Old 07-10-2017, 07:58 PM   #3
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Re: Transmission making me Crazy....

I beleive that should have the 4l60e transmission. They have notoriously high failure rates. Found that out after my brother's Trailblazer randomly failed for no reason with 90k miles on the clock. Found a guy who rebuilds them on a regular basis and sells a few a month because of the high failure rates.
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Old 07-10-2017, 08:39 PM   #4
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Re: Transmission making me Crazy....

Keep in mind all the famous 1870 code was often caused by a worn control valve bore in the valve body causing in internal pressure loss in the tcc control circuit, very common issue.
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Old 07-10-2017, 09:14 PM   #5
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Re: Transmission making me Crazy....

In 2002 Hydramatic finally started heat treating the reaction shell hub splines. The other weaknesses are direct clutches in less-than V-8 applications which may have a thicker spacer instead of a full compliment of frictions and steels. The early-on cast oil pump hubs which didn't like higher RPM and less than 10 vane pumps were gone by 2000. Aside from that, the trans in its basic form will take 350 ft/lb pretty consistently, and a lot more if higher quality parts are selected.
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Old 07-10-2017, 09:16 PM   #6
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Re: Transmission making me Crazy....

Quote:
Originally Posted by maxwedge View Post
Keep in mind all the famous 1870 code was often caused by a worn control valve bore in the valve body causing in internal pressure loss in the tcc control circuit, very common issue.
This is a well publicized condition, but similar symptoms occur after neglect and lack of regular changes. If the bore is not egged, cleaning sludge can improve the conditions. If not, it makes life for the rebuilder a little easier.
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Old 07-10-2017, 09:23 PM   #7
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Re: Transmission making me Crazy....

Thanks for all of the info. I just got back from a test drive since my husband replaced that solenoid. So far, no hard shifting. He said the fluid he drained when he started looked a little burnt, so there's no telling how long it's been since the trans was serviced. At this point I'm going to keep my fingers crossed, and if I still have problems, I'll likely have the valve control body replaced completely.
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Old 07-15-2017, 03:10 PM   #8
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Re: Transmission making me Crazy....

I've had the vehicle back at the car lot for the last few days, and the owner swore it was fine, says he's not seeing the problem I reported. I picked it up today, and literally 5 minutes on the freeway (again!) the SES light came on. I turned around and went back. Their reader showed the same code, so he test drove it. Upon his return, he acknowledged the hard shift and believes it's because either the fluid was overfilled or had the wrong kind of fluid. He says leave it with him a few more days and he'll fix it.
The neighbors across the street from us own and run their own race cars, fixing them up in their garage themselves. On a hunch, I just walked over and explained what was happening. All three said it was either the converter or front transmission pump. Either way, I'm looking at at least $1000 worth of further repairs.
I'm inclined to believe them, even if they've never driven it, because they rebuild all of their own transmissions, and would have no reason to lie to me. So I guess what I'm wanting to know is if I should put it in the shop, again, and hope that is all that is wrong with it, or could I drive it and just ignore the hard shift in the lower gears?
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Old 07-16-2017, 10:01 AM   #9
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Re: Transmission making me Crazy....

Again had that code in my TB, was the valve body problem, careful on the advice your are receiving, drove it for 20 k with no issues other than the hard shift and code. Then fixed it with a Sonnax repair kit for the valve body.
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Old 07-16-2017, 11:34 AM   #10
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Re: Transmission making me Crazy....

Quote:
Originally Posted by Crazygirl View Post
All three said it was either the converter or front transmission pump. Either way, I'm looking at at least $1000 worth of further repairs...

I'm inclined to believe them, even if they've never driven it, because they rebuild all of their own transmissions, and would have no reason to lie to me.
Just one opinion, but I would be inclined to dismiss the neighbor's diagnosis.

I rebuild my transmissions as well (including transverse). First, a converter problem would likely exhibit a lot of other symptoms. Those include noise, high temperature, slipping while IN ranges, metal pieces in the pan, and others.

Second, a "front pump" is a bit redundant, and may provide some hints about their level of knowledge of the 4L60/65. There is only one pump. If they believe there is a rear pump they probably haven't opened a transmission since the 1960s. Further, pump failures most commonly result in lower line pressure or foamy (air-entrained) oil, not higher line pressures. The symptoms of a harsh shift would not occur with lower pressure, but slippage and slow/long shifts would be apparent.

I'll stick with the original suggestion that the pressure control/valving would be the most common problem. Max defined that even further., but since changing the PCS also involved dropping the pan and changing the fluid/filter, there is a possibility that the valve spools are varnished/sludged and not otherwise damaged. In this case, running the fluid and changing it again after it has had an opportunity to clean things up could potentially help the condition.

There is also an equal chance that the valve body has the common wear, and reaming/sleeving it will solve the problem. If you DO decide to repair or replace the valve body with a remanufactured unit, be sure to replace the separator plate at the same time since its integral check ball seats do tend to take a beating over time and could contribute to shifting problems.

As Max indicated, driving it for a while with the harsh shifts should not be a substantial problem (20K miles), and may allow the clean oil to free up some sticky spools.

Incidentally, the transmission WAS refilled with Dexron 6 fluid, right? Dexron 3 is no longer permissible in these units.
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Old 07-16-2017, 03:29 PM   #11
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Re: Transmission making me Crazy....

Quote:
Originally Posted by Blue Bowtie View Post
Incidentally, the transmission WAS refilled with Dexron 6 fluid, right? Dexron 3 is no longer permissible in these units.
A 2002 transmission was spec'ed with Dex III.

My '03 Trailblazer was, and will be, refilled with "Dex/Merc" (Dex III substitute)
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Old 10-22-2017, 05:16 PM   #12
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Re: Transmission making me Crazy....

Update time. So, I bought the TB on 6/30 and FINALLY got it back yesterday. Long story on why it took so long, but the dealer owner said they bought some kit for the transmission that had to be bored out to fit, and said a trans line had a small hole burned into it because of where Chevy chose to install it and said that's why I was losing transmission fluid. Drove it for short while last evening, had no problems. Drove it for most of the day today, and it performed like it should. Get 5 miles away from home, and it started doing the hard shift between gears again. No SES light but the jerking feeling and clunking sound is pretty distinctive. I'm beginning to think it would be better just to get rid of it altogether. Thoughts?
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